Provided is a post-processing device including a stapling unit that performs stapling on a sheet bundle with a driving force caused by a rotation of a motor, a power supply unit that supplies power only to the motor, a sheet bundle detector that detects presence or absence of the sheet bundle which is inserted into the stapling unit, and a stapling time storage unit that stores an execution time of one session of the stapling, wherein the power supply unit initiates power supply to the motor based on a detection result of the sheet bundle detector and stops supplying the power to the motor after an elapse of a predetermined time which is stored in the stapling time storage unit.